Bassist David Ellefson was fired from Megadeth back in May after a highly-publicized sexual affair. Megadeth has since removed Ellefson's bass parts from their new album and had a currently unknown bassist (rumored to be Steve Di Giorgio of Testament) re-record them.
Ellefson recently confirmed he doesn't have a copy of the new album with his bass parts on it, though he's not really sure why the band felt the need to remove him from it in the first place.
"They did what they did," said Ellefson said in an interview with The Metal Voice. "I don't think they had to do that. I asked them not to. But they did what they did. It's the path they chose." He later added that "I don't have any ill will toward [Megadeth guitarist and vocalist Dave Mustaine] or [the band]. I really don't."
Megadeth has not yet announced an official replacement for Ellefson, but did have ex-bassist James LoMenzo filling in for him live. LoMenzo originally played with Megadeth between 2006 and 2010. Ellefson has since formed a new band called The Lucid.